1781661625 has 16 divisors (see below), whose sum is σ = 2354311440. Its totient is φ = 1341484800.

The previous prime is 1781661617. The next prime is 1781661653. The reversal of 1781661625 is 5261661871.

It can be written as a sum of positive squares in 8 ways, for example, as 487173184 + 1294488441 = 22072^2 + 35979^2 .

It is not a de Polignac number, because 1781661625 - 2³ = 1781661617 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 417090 + ... + 421339.

It is an arithmetic number, because the mean of its divisors is an integer number (147144465).

Almost surely, 2^1781661625 is an apocalyptic number.

It is an amenable number.

1781661625 is a deficient number, since it is larger than the sum of its proper divisors (572649815).

1781661625 is an equidigital number, since it uses as much as digits as its factorization.

1781661625 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 838461 (or 838451 counting only the distinct ones).

The product of its digits is 120960, while the sum is 43.

The square root of 1781661625 is about 42209.7337707785. The cubic root of 1781661625 is about 1212.2952642588.

The spelling of 1781661625 in words is "one billion, seven hundred eighty-one million, six hundred sixty-one thousand, six hundred twenty-five".